I've had quite a lot of bounces recently. This seems largely to have been because my hosting company was having difficulty sending to Outlook (and therefore maybe Microsoft servers generally). But I've been taking more interest in the bounce messages as well.

These have included "Rejected by header based Anti-Spoofing policy" (an organisation using Mimecast recognising its own email address in the From: header), "DMARC Verification Failed" for a domain with p=reject (despite dmarc_moderation_action being Munge From), "This email has been delivered to the intended recipient, but our email system has identified that DKIM Signing is missing or has been misconfigured. Please ask your IT department to configure DKIM Signing to allow us to confirm the authenticity of your emails." (despite the hosting company having the right DKIM record) and more.

I have added REMOVE_DKIM_HEADERS = Yes to mm_cfg.py and restarted Mailman, and changed from_is_list from No to Munge From.

Nobody seems to mind that all emails are now from the list address - reply_goes_to_list was already set to This list, and now the sender's own email address now appears in the Cc: header.

Is there anything I could do as well as or instead of that?

Thanks

Jonathan